Catalysts for the addition polymerization of unsaturated organic compounds



atenteoi Nov 6, H945 CATALYSTS FDR COOS a r annrrrou roarza'rron or pusa'r t: rap oaac William D. Stewart, Amen, (Ohio, assignor to The E. ii. Goch Company, New York, N. Y a corporation oi New York No Drawing. Application April 15, 1942, Serial No. 439,191

M Cla.

This invention relates to the polymerization of unsaturated organic compounds which are capable of undergoing an addition polymerization to form high molecular weight linear polymers and particularly to the polymerization in aqueous emulsion of a butadiene-1,3 either alone or in admixture with a monomer copolymerizable therewith. The principal object of the invention is to provide a new class of catalysts or accelerators for such polymerizations by the use of which improved polymers are obtained in increased yield and in a much shorter interval of time.

I have discovered that the time required to effect addition polymerization reactions can be greatly reduced by the use of heavy metal catalysts and that the polymers produced when employing such catalysts exhibit excellent properties despite the short periods of time required for the completion of the polymerization. Certain of these heavy metal catalysts, called redox systems because of their property of catalyzing biological oxidation-reduction reactions, are disclosed in my copending applications Serial Nos. 379,712 to 379,717 inclusive, filed February 19, 1941.

This application is a continuation-in-part of my copending application Serial No. 379,714 and relates to the class of heavy metal catalysts derived from a heavy metal compound and an aliphatic carboxylic acid containing at least one carboxyl group and in addition at least one primary amino group in the alpha position with respect to a carboxyl group and no additional types of substituents other than hydroxy groups. Such amino acids will, in general possess the formula wherein R represents hydrogen, a hydrocarbon radical or a hydroxy, carboxy or amino substitutedhydrocarbon radical. Typical amino acids included in this class are glycine (amino-acetic acid), alanine (alpha-amino-propionic acid), serine (alpha amino beta hydroxy propionic acid), threonine (alpha-amino-beta-hydroxy-butyric acid), valine (alpha-amino-isovaleric acid), leucine (alpha-amino-isocaproic acid), nor-leucine (alpha amino caproic acid), isoleucine (alpha-amino-beta-methyl-beta-ethyl propionic acid), aspartic acid (alpha-amino-beta-carboxypropionic acid or amino-succinic acid), glutamic acid (alpha-amino-gamma-carboxy butyric acid or alpha-amino glutaric acid), lysine (alphaepsilon-diamino caproic acid) and the like.

The term heavy metal is used herein to sigcurve.

niiy metals which have a density greater than four, an atomic weight greater than forty and a low atomic volume (ratio -of atomic weight to density) and consequently appear substantially at or near the minimum points above an atomic weight, of forty on Lothar Meyers atomic volume (See any standard textbook of Inorganic Chemistry such as Ephraims Textbook of Inorganic Chemistry" page 30 or Caven and Landers Systematic Inorganic Chemistry" facing page positions of the long periods of a periodic table arranged in long and short periods, and especially those occurring in the 6th to 12th positions of the long periods (considering the alkali metals to occupy the first position and all the rare earth metals to occupy a single position), that is, the elements occurring in group VIII of the Mendelef Periodic Table such as iron, cobalt and nickel, those in subgroup B of groups I and II of the Mendelef Periodic Table such as copper, zinc and mercury and those in subgroup A of groups VI and VII of the Mendelef Periodic Table such as :chromium, manganese and molybdenum.

The heavy metal catalysts of this invention are derived from a heavy metal compound and an amino acid of the type described, and may consist of complex compounds containing a heavy metal atom united to one or more amino acid residues at least in part by coordinated covalences rather than primary valences as in the complex compound copper-glycine which is believed to have The heavy metal catalysts may also consist however of simple heavy metal salts of amino acids or oi'mixtures of heavy metal salts and amino acids or amino acid salts. In the latter event, the heavy metal salts may combine chemically with the amino acids to form complex compounds of the type described above, but it is to be understood that all catalysts obtained by the combination of heavy metal compounds and amino acids of the type described are included in this invention regardless of whether or not known chemical complexes are formed. The preferred catalysts are obtained from salts of those heavy metals which are known to occur in living cells, particularly those occurring in the 6th to 12th positions (i. e., in group VIII, I-B, II-B, VI-A, and VIL-A) oi the first long period of the periodic table, and

2 asses-la from amino acids or hydroxy substituted amino acids containing less than eight carbon atoms. examples of such preferred catalysts being iormed from mixtures of simple salts of iron, cobalt. nickel, zinc and copper with glycine, alanine and serine. Since the polymerisation reactions cats. lyzed by the method of this invention are preferably carried out in aqueous emulsion it is also highly desirable that the catalysts be water soluble, by which is meant that the whole catalytic ent in the emulsion. The preferred catalytic combinations mentioned above are readily soluble in water when the heavy metal salt employed is a nitrate, chloride, sulfate or other water soluble salt and when the amino acid is employed as such or as an alkali metal salt.

In the practice oi this invention addition poly- I merisations of unsaturated organic compounds to form high molecular weight linear polymers are preferably carried out in aqueous emulsion in the presence of the above-described heavy metal catalysts although other methods of polytil polymer is formed. The resulting polymerised emulsion containin P lymer particles dispersed in water greatly resembles natural rubber latex and may be co lflsted in the usual manner to yield the solid polymer.

The amount of the catalyst to be used in the polymerization maybe varied over rather wide limits depending upon the particular catalyst used and the particular compounds polymerized but, in general, only very small or catalytic amounts are employed and it is preferable that no more than about 2% by weight,based on the weight of the monomers, of the whole catalytic system. including both the heavy metal compound and the amino acid. if a mixture of these is employed a the catalyst. be used. when the catalyst consists of a complex compound, containing a heavy metal atom united to one or more amino acid molecules, added as such, or of a heavy metal salt of an amino acid added as such. amounts of 0.1 to 1% of the catalyst are preferred when, however, the catalyst is added as a mixture of a heavy metal salt and an amino acid, amounts of 0.01 to 0.1% of the heavy metal salt and 02 to 1.5% of the amino acid give best results. Although ionlsable heavy metal salts, particularly those 'of cop er and manganese, when present in polymerization batches not containing a compound which forms a complex therewith, often inhibit polymerizations rmless their concentration is less than 0.1%, the catalysts of this invention do not this disadvantage since the presence of the amino acid converts the heavy metal ions into complexes in which the heavy metal atoms are present in a substantially un-ionized form.

As has been mentioned hereinabove the heavy metal catalysts of thisin'vention may be used generally in the polymerization of those unsaturated organic compounds which undergo addition polymerizations toiorm high molecular acrylonitrile,

a large number monomer molecules add onto one another to form a large molecule having a predominantly linear structure. Unsaturated organic compounds which undergo such polyl merisationsgenerally contain the characteristic structure and, in most cases. have at least one of the system will dissolve in the amount of water pres-- connected valencies attached to an electronegative group, that is, a group which increasesthe polar character of the molecule such as a chlorine group or an organic group containing a double it or triple bond such as vinyl, phenyl, nitrile, carboxy or the like. Included in this class of monomers are the coniugated hutadienes or butadienes-1,8 such as butadiene (butadiene-i,8), 3,8-

dimethyl butadiene-LS, isoprene, chloroprene,. 20 plperylene, a-furyl butadiene-l,3, a-methoxy butadiene-1,3 and-the like: aryl olenns such as styrene, p-chloro styrene, p-methoxy styrene, alphs-methyl styrene, vinyl naphthalene and the like; acrylic and substituted acrylic acids and 25 their esters, nitriles and amides such as acrylic acid, methacrylic acid. methyl acryiate, ethylacrylate, methyl alpha-chloro-acrylate, methyl methacrylate, ethyl methacrylate, butyl moth-- acrylate, methyl ethacrylate. i lylonitrile, methmethacrylamide and the like, methyl isopropenvl ketone, methyl vinyl hetonc, methyl vinyl ether, vinylethlnyl alhl carbinols, vinyl acetate, vinyl chloride, vinylldene chloride,

' vinyl furane, vinyl carbasole, isobutylene, vinyl acetylene and other unsaturated hydrocarbons,

esters. alcohols, acids. ethers, etc., of the type described.. Such unsaturated compounds may ,be polymerized alone, in which case simple linear polymers are formed,- or mixtures of two or more a of such compounds which are copolymerisable with each other may be polymerized to form linear copolymers.-

The catalysts of this invention are particularly elective when the monomeric material polymer.

55 compounds mentioned hereinabove. In this case theproductsofthepoly'merlsationarehighmolecular weight linearpolymers and copolymers.

which are rubbery in character and may be called synthetic rubber. Thepolymerlsation cl 1 other monomers and monomer mixtures of the type described to form linear polymers 01' a resinous character is also improvedhowever, by the catalysts of this invention. W

As emulsifying agents which may be employed in emulsion polymerizations may be mentioned soaps such as sodium oleate, potassium palmitate and sodium myristate'synthetic saponaceous materials including hymolal sulfates and alkaryl sulfonates such as sodium lauryl sulfate and sodium isopropyl naphthalene sulfonate, and salts of organic bases containing long carbon chains such as trimethyl-cetyl-ammoniuxn methyl sulfate, the hydrochloride of oleylamidoethyl dimethyiamine, the hydrochloride of diethylaminoethyl-oleyb weight linear polymers by which is meant that amide thelike. The soaps are employed in aeeaara polymerizations under basic conditions, the salts of organic bases under acid conditions and the synthetic saponaceous materials under acid, alkaline or neutral conditions.

Polymerization initiators which are preferably, although not necessarily, employed in the polymerization batch together with the heavy metal catalysts oi this invention include per-compounds such as hydrogen peroxide, benzoyl peromde, po-' tassium persulfate, sodium perborate, potassium percarbonate and the like as well as other types of initiators such as diazoaminobenzene, sulfur dioxide, dipotassium diazomethane disulfonate and triphenylmethylazobenzene. The per-compounds, particularly hydrogen peroxide when used with a fatty acid soap as the emulsifying agent, give especially good results in the emulsion polymerization. of conjugated butadienes in the presence of combinations of heavy metal salts and amino acids as catalysts.

It is also desirable in the emulsion polymerization of conjugated butadienes to form synthetic rubber, to employ a polymerization modifier which increases the plasticity and solubility of the rubber polymers produced. Compounds suitable for this purpose include sulfur-containing compounds such as dialkyi dixanthogens, the higher tetraalkyl mono and polysulfides, mercaptoalkyl thiazcles and the like.

The preferred manners of practicing this invention and the improved results obtained thereby may be shown by the following specific examples which are intended to illustrate rather than limit the invention. The parts are by weight.

Example I A mixture of 55 parts of butadiene and 45 parts of acrylonitrile is emulsified in 250 parts of a 2% aqueous solution of myrlstic acid which is 85% converted into soap by neutralization with sodium hydroxide. parts of a 3 /2% solution of hydrogen peroxide, 0.3 part of a polymerization modifier, di-isopropyl dixanthogen, and a heavy metal catalyst consisting of a mixture of 0.01 part of cuprous chloride and 0.50 part of glycine are added to the emulsion and the emulsion is agitated at 30 C. until polymer is formed. The polymerization is completed in 23 hours to yield 94 parts of a rubbery copolymer of butadiene and acrylonitrile. A similar polymerization in which no heavy metal catalyst is employed requires 45 hours for completion and is only 45% complete after 23 hours and another similar polymerization employing cuproms chloride, but no glycine, has not started after 45 hours. The solubility and plasticity of the rubbery copolymer prepared in the presence of the copper-glycine catalyst is equal to that of the polymer prepared in the absence of the catalyst, and the vulcanizates obtained from the polymers prepared in the presence of the catalyst possess higher tensile strengths and ultimate elongations than similar vulcanizates from the polymers prepared in the absence of the catalyst,

Example I! A mixture of 13 parts by weight of butadiene and '7' parts by weight of acrylonitrile is agitated is completed after about 86 hours and a concen trated latex containing about 18 parts of a rubbery copolymer of butadiene and acrylonitrile dispersed in only about 20 parts of water is obtained. The preparation of such concentrated laticesin the absence of heavy metal catalysts requires very long reaction times and is sometimes impossible. The concentrated latex obtained may be dried to yield exceedingly tough, oil-resistant, synthetic rubber films or it may be coagulated to yield a plastic, oil resistant synthetic rubber.- The synthetic rubber obtained by the latter procedure may be compounded and vulcanized to yield especially strong resistant vulcanizates having tensile strengths oil well over 5000 lbs/sq. in; and ultimate elongations over 900%.

Example I]! An emulsion of a mixture of butadiene and acrylonitrile is prepared as in Example 1, except that the heavy metal catalyst consists of a mix ture of 0.03 part of iron sulfate, 0.01 part of cobaltous chloride and 0.25 part of serine, and is polymerized in 20 hours at 30 C. The product is a synthetic latex which may be coagulated in the usual way to yield a plastic, coherent, oil resistant synthetic rubber. It was also observed that the productobtained in this example possessed considerably more tack, and better milling characteristics on a hot mill than is ordinarily found in butadiene acrylonitrile copolymers.

Example IV Example 111 is repeated using alanine as the amino acid in place of serine. In this example the polymerization requires 26 hours to produce a 90% yield of a similar rubbery butadiene acrylonltrile copolymer. The times required to effect the polymerization in this and the preceding example are to be comparedwith a time of 45 hours to complete the polymerization whenno heavy metal catalyst is employed, thus again showing the remarkable accelerating effect of the catalystsof this invention on the polymerization.

Emmple V The procedure of Example m is again repeated using as the heavy metal catalyst a mixture of .03 part of iron sulfate, .01 part of cobalt chloride and 0.25 part of glutamic-acid. The polymerize tion requires only 14 hours to produce a 91% yield of a synthetic rubber similar to that obtained in mample 111.

Example VI an emulsion containing the following ingredients is prepared:

Parts Butadiene 70 Styren Sodium myristate (2% aqueous solution)- 250 Hydrogen peroxide .35 Di-isopropyi dixanthogen .45 Ferrous ammonium sulfate .05 Serine .50

monomers in place oi styrene similar synthetic rubbers are obtained in good yields in about the same length oi time. The proportions oi the monomers polymerized may also be varied without appreciably aflecting the length oi time required for the polymerization. For example a monomer mixture consisting oi 90 parts oi styrene and parts oi butadiene maybe polymerized in this same manner in about hours to produce a strong, iienible, thermoplastic synthetic resin. Other thermoplastic resins may be obtained by using styrene, methyl methacrylate, vinyl chloride'or the like alone or in admixture with each other as the polymerizable material.

Other embodiments oi the invention in which various other heavy metal catalysts are with various monomer mixtures, initiators and emulsiiying agents also demonstrate that the polymerization velocity is remarkably increased by the practice oi this invention.

The use oithe heavy metal catalysts oi this invention is particularly important in the commercial manufacture oi polymers since the great accelerating ei'iect of these catalysts more than counteracts the inhibiting eiiect oi other substances which may be present during the polymerization. Many such inhibiting substances are quite diiiicult to exclude irom the polymerization batch because they may be present as impurities in the monomers or in other essential materials. Moreover other substances which it is highly desirable to include in the polymerization recipe,

such as certain polymerization modifiers, also oiten retard the speed or the polymerization but when used with heavy metal catalysts the polymerizstion takes place in a convenient interval oi time. I

Other methods and procedure known to be useiul in connection with the polymerization oi unsaturated organic compounds are within the spirit and scope oi the invention as deiined in the appended claims;

- I claim: v

1. The method which comprises subjecting a monomeric material comprising a conjugated butadiene, to polymerization in aqueous emulsion sion in the presence iii a water'soluble salt oi a] heavy metal occurring in group VIII: and the iirst long period oi the periodic table, and a saturated aliphatic carboxylic acid having a primary oi a heavy metal catalyst obtained by the combination oi a water soluble heavy metal salt and a saturated aliphatic monocarbonylic acid containingaprimaryamlnogroupattached-tothe same carbon atom to which is attached the carbonyl group and being otherwise composed, in addition to the primary amino group and the carbonyl group, oi saturated aliphatic structure in which there is present, in addition to hydrocarbon structure, no structure other than hydroxy.

4. The method which comprises subjecting a monomeric mixture oi butadiene and a compound which contains group. and is c ll lymerizable therewith in aqueous emulsion, to polymerization in aqueous emulsion in the presence oi a water soluble salt oi a heavy metal occurring in group VIII and the iirst longperiod or theperiodic table, and a saturated aliphatic monocarbonylic acid containing less than eight carbon atomathe said acid having a primary amino groupv attached to the'same carbon atom to which is attached the carbonyl group and being otherwise composed, in addition to the primary amino group and the carbonyl group, oi saturated aliphatic structure in which there ispresent, in addition to hydrocarbon structure, no structure other than hydroxy.

in the presence oi a heavy metal catalyst. ob-

tained by the combination oi a water-soluble heavy metal salt and a saturated aliphatic carboxylic acid selected irom the class consisting oi saturated aliphatic carbonylic acid having a primary amino group in alpha position to a carbonyl group and being composed, in addition to primary amino and carbonyl, oi saturated aliphatic structure'made up exclusively oi atoms oi carbon, hydrogen and ongen, all oxygen being present in hydrony, and saturated aliphatic carboxylic acids having a primary amino group in alpha position to a carbonyl group and being composed, in addition to primary amino and carboxyl. of saturated aliphatic structure made up w exclusively oi atoms of carbonand hydrogen.

2. The method which comprises subiectin'g a monomeric mixture oi as conjugated butadiene and anothercompound which contains a group and is copolymerlzable themmth in aqueous emulsion, to polymerization in aqueous emul- 5. The method which comprises subjecting a monomeric mixture piv butadiene and a compoundwhichccntainsa I CBC group and is coplymeriaable therewith in aqueous emulsion, to polymerisation in aqueous emulsion in the presence oi a water soluble salt oi aheavymetal occurringingroupvmand the 'ilrst long period or the periodic table. and a saturated aliphatic monocarboxylic acid containing less than eight carbon atoms, the said acid having a primary amino group attached to the same carbon atom to which is attached the carboxyl group and being otherwise composed, in addition to the primary amino group and the carbonyl group, exclusively oi saturated aliphatic hydrocarbon structure.

6. The method of claim 5 wherein the monomeric mixture polymerized consists oi butadiene and acrylonitrile.

I. The method which comprises. polymerizing a mixture oi butadiene and acrylonitrlle in aqueous emulsion in the presence oi a water soluble iron salt and alanine.

8. The method which comprises subjecting a monomeric mixture oi butadiene and a compound! which contains a 15 group and is copolymeriaable therewith in aqueaseasva ous emulsion, to polymerization in aqueousemulsion in the presence of a water soluble salt of a heavy metal occurring in group VIII and the first long period of the periodic table. anda saturated aliphatic monocarboxylic acid containing less than eight carbon atoms, the said acid having a, primary amino group attached to the same carbon atom to which is attached its carboxyl group, a hydroxy group attached to another carbon atom and being otherwise composed, in addition to the carboxyl group, the primary amino group and the hydroxy group. exclusively of saturated aliphatic hydrocarbon structure.

9. The method of claim 8 wherein the monomeric mixture po ymerized consists of butadiene and styrene.

10. The method which comprises subjecting a mixture of butadiene and a compound containing a group which is copolymerizable therewith in aqueous emulsion to polymerization in aqueous emulsion in the presence of a water soluble salt of a group VIII heavy metal and serine.

11. The method which comprises polymerizing a mixture of butadiene and styrene in aqueous emulsion in the presence of a water soluble cobalt salt and serine.

12. The method which comprises polymerizing a conjugated butadiene in aqueous emulsion in the presence or a heavy metal catalyst comprising the complex compound copper glycine.

13. The method which comprises polymerizing l.

a conjugated butadiene in aqueous emulsion in the presence of a water soluble complex compound. of a heavy metal occurring in the 6th to 12th positions of the first long period of the periodic table and a saturated aliphatic monocarboxylic acid containing a primary amino group in alpha position to its carboxyl group and being otherwise composed, in addition to the primary amino group and the carboxyl group, of saturated aliphatic structure in which there is present, in addition to hydrocarbon structure, no structure other than hydron.

14. The method which comprises polymerizing butadiene in aqueous emulsion in the presence of hydrogen peroxide, a fatty acid soap, and a heavy metal catalyst obtained by the combination of a water soluble salt of a heavy metal occurring in group VIII and the first long period of the periodic table and a saturated aliphatic carboxylic 

